ABSTRACT
After gaining access to the systemic circulation through one of the routes of administration, xenobiotics distribute in different tissues and organs of the body. Depending on their physicochemical characteristics, a series of physical and physiological processes occur simultaneously that shape the distinctive pattern of their distribution in the body. An example of physical processes is the simple dilution of drug or toxin in the intracellular and extracellular uids and the examples of physiological processes are protein binding, tissue uptake, permeation of the compound through different biological barriers in the body, interaction with transport proteins in conjunction with the processes of metabolism, and excretion. The distribution processes transfer the compound to various regions of the body including the receptor sites, target organs, excretory organs, and other tissues. Thus, if the compound is not actively or passively targeted to a receptor site in the body, all organs and tissues will have to endure the presence of the xenobiotic. The subject of targeting the therapeutic agents is beyond the scope of this book.
